1. Field of Invention
The invention relates to a system and a method for controlling the drive of a vehicle and a program therefor.
2. Description of Related Art
In vehicle drive systems (power trains) including generator motors between engines and transmissions, the rotors of the generator motors are joined between the engines and the input shafts of the transmissions and the stators are disposed radially outside the rotors. In the vehicle drive systems, the torque of the generators, or generator torque, can be transmitted to the engines to start them by using and driving the generator motors as a motor and electrical energy can be generated by using the generator motors as a generator and collecting the rotational energy of the rotors.
In hybrid-vehicle drive systems including planetary gear units, for transmitting the torque of the engine, or part of the engine torque, to generators, and transmitting the remaining to driving wheels together with the torque of drive motors, or drive-motor torque, carriers and the engine are joined together, ring gears and driving wheels are joined together, and sun gears and the generators are joined together. In the vehicle drive systems, the generator torque generated by using and driving the generators as a motor is transmitted to the engine to start the engine and electrical energy can be generated by collecting the rotational energy of the rotors of the generators in an overdriven condition.
A vehicle-drive control system is provided in which a crank angle at engine stop is recorded as a stop crank angle when the position of the crankshaft, which is the rotating position of the engine 11, is expressed as an angle from a specified reference point (hereinafter, referred to as a reference point), namely, a crank angle, and in which the generator motor is driven to start the engine at engine startup to rotate the crankshaft from the stop crank angle to a crank angle best suited to start the engine, namely, an optimum crank angle. See, for example, JP-A-2001-221138.
In this case, however, because it is necessary to rotate the crankshaft to the position of the optimum crank angle at the start of the engine, not only the engine start timing is delayed correspondingly but also an uncomfortable feeling may be produced in the occupant of the vehicle.
Accordingly, a vehicle-drive control system is provided in which a generator motor is driven to control the brake when the drive of the engine is stopped, with the position of the optimum crank angle as target stop position, to stop the engine at the target stop position as found, for example, in JP-A-9-264235.
FIG. 2 is a time chart for the operation of the conventional vehicle-drive control system. When the ignition switch is turned off to turn an ignition switch SGig from on to off at timing t1, the fuel injection control and ignition control in the engine are stopped. Although the engine thereafter continues to rotate by inertia, the engine speed NE decreases gradually by friction. When the engine speed NE becomes lower than, for example, 100 rpm, the system waits until the value of the counter indicating a crank angle reaches a start count value indicating the position to start preset brake control. When the count value reaches the start count value at timing t2, the brake control by the generator motor is started. The start count value is set so as to be within the range indicating an optimum crank angle when the engine speed NE reaches 0 rpm.
The engine speed NE decreases with the brake control, and when the engine speed NE reaches 0 rpm at timing t3, the brake control is finished. In this way, the engine is stopped at a target stop position.